General analytical treatment of the flow field relevant to the interpretation of passive fluxmeter measurements

Relevant flow dynamics for the interpretation of passive fluxmeter (PFM) measurements are investigated by determining the properties of the flow field inside the PFM and its relationship to the undisturbed ambient fluxes in the aquifer. The flow domain is treated in two dimensions and consists of a system of concentric annular filter zones of different radii and hydraulic conductivities. Flow inside the PFM is shown to be uniform regardless of well configuration. Analytical expressions quantifying flow convergence are derived for an increasing number of rings, validated against numerical modeling and used to perform a sensitivity analysis. One of the derived convergence relationships is embedded in an inverse model to estimate aquifer and well screen conductivities and ambient groundwater and methyl-tertiary-butyl-ether ( MTBE) fluxes in the Borden Aquifer under controlled flow conditions. Results compare well to independent estimates when the method of quantifying convergence is consistent with field conditions.